A casement window has a window sash which is movably mounted within a frame by a pair of hinges mounted between the window frame and the top and bottom of the window sash. Normally, the arrangement is one in which there is a track which is mounted on the window frame and a sash arm is connectable to the window sash. The support arm interconnects the track and the sash window; the support arm is pivotably connected to the sash arm and to the track. The sash arm is pivotably connected to a mounting shoe which is supported and guided for movement lengthwise of the track.
It is also well known in the art to provide an intervening link between the sash arm and the movable shoe to provide for an offset sash arm. Such an arrangement typically includes a second intervening length between the support arm and the movable shoe to provide further support.
Casement window operators typically include a hand crank which drives a worm gear arrangement. In turn, the worm gear arrangement is connected to an arm or lever which pushes the window sash open. The worm gear assembly typically includes a gear shaft having the worm at one end thereof with the other end of the gear shaft extending outwardly through the housing to engage a crank. When the crank is turned, the worm causes the worm wheel to rotate and this in turn causes the sash to pivot on its hinges between open and closed positions.
There are several different arrangements for casement windows. A first arrangement utilizes a single arm operator which has an arm which pivots about an axis that is fixed with respect to the window frame and worm gear. The remote end of the arm carries a bearing which slides in a track mounted to the underside of the sash. One disadvantage with such a single end operator is the torque required to move the sash towards its fully open position.
An improvement on the single arm operator is the split arm variety. A split arm operator includes a second end which has a pivot point in the middle of the second arm and a remote end of the second arm is secured to a pivotable mounting to a fixed point on the sash. While the split arm operator allows the window to extend to its fully open position, it does present some difficulty at the time of the initial opening of the sash.
A further type of window operator is a dual arm operator which has one arm which rotates around a fixed axis and a housing which carries at its far end a bearing to slide in the track mounted to the window sash. This arrangement includes a second arm which has a pivot joint and which is secured at its remote end by a pivotable but fixed connection to the sash.
One of the problems associated with the above operators is an eventual loosening of the attachments within the housing due to the torque generated by the worm gear.